watchdog and lemming board interference

[ArcticSnow]

There seem to be unwanted interference in between the watchdog and the lemming board. With certain lemming board, the watchdog cannot be activated. If it is then the whole mote freezes. If deactivated the mote starts and run but the whole I2C line is down. This happens to certain lemming board, but not all. For instance out of the 10 stations deployed in Finse in MArch, 4 of them have the issue now. I tried switching the waspmote, but the problem occurs when plugging the lemming.

[jdavid]

This issues may be related to the number of issues we've had with the I2C/RTC and SD.

It seems to be hardware, but let me know if you think there's something I can do, maybe some software workaround is possible. Can you reproduce it systematically? When does it freeze exactly? Is there some output in the logs/usb?

At the hardware level, something we've talked before and that may help, is to use an I2C isolator, nowadays most Libelium's shields with I2C have one.

[jdavid]

As reported by e-mail, this may be solved with new hardware including an I2C isolator:

1- I2C isolation. We discovered the hard way that any grounding occuring on the I2C line leads the waspmote to complete random behavior, in many instances fatal to the logger. Adding this little component will prevent such behavior and is quite straight forward to implement

3- Some interference in between the watchdog and the I2C bring some fatal problem to the system. However, this is not occuring on all waspmotes, and occured in many instances past deployment. Once this problem arise, we have not figured a way to solve the problem. We hope that the I2C isolator can prevent this problem in the future.

The I2C isolator will require software support, but first we need the hardware part.